1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device. In particular, one embodiment of the present invention relates to a semiconductor device including an oxide semiconductor.
Note that one embodiment of the present invention is not limited to the above technical field. For example, one embodiment of the present invention relates to an object, a method, or a manufacturing method. Further, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Further, one embodiment of the present invention relates to a memory device, a processor, a driving method thereof, or a manufacturing method thereof.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. Thus, a semiconductor element such as a transistor or a diode and a semiconductor circuit are semiconductor devices. A display device, a light-emitting device, a lighting device, an electro-optical device, an imaging device, an electronic device, and the like may include a semiconductor element or a semiconductor circuit. Therefore, a display device, a light-emitting device, a lighting device, an electro-optical device, an imaging device, an electronic device, and the like include a semiconductor device in some cases.
2. Description of the Related Art
A technique for forming a thin film transistor with the use of a semiconductor thin film formed over a substrate having an insulating surface has been attracting attention. A thin film transistor is used for a display device typified by a liquid crystal television. A silicon-based semiconductor material is known as a material for a semiconductor thin film applicable to a thin film transistor. As another material, an oxide semiconductor has been attracting attention.
As a material for the oxide semiconductor, zinc oxide or a substance containing zinc oxide is known. Thin film transistors each of which is formed using an amorphous oxide (an oxide semiconductor) having an electron carrier concentration of lower than 1018/cm3 are disclosed (Patent Documents 1 to 3).